Not applicable.
Not applicable.
1 . The Field of the Invention
This invention relates to elongated cable bolts useful for installation, with cooperating resin systems, in boreholes in underground mines, to achieve ground control and, when installed in mine roofs, are useful, in combination with trussing systems, support plates and the like, for delimiting dilation of mine roofs, thereby contributing to safety of workmen and machinery and deterring mine roof collapse. In particular, the invention pertains to designing cable bolt proximal ends and torque-applying devices therefor, for permitting the application of both axial thrust and also torque to cable bolts, to thrust these into boreholes and simultaneously axially spin the cable bolts so as to mix to desired degree, and without over-mixing, the pre-implanted resin systems within the boreholes, whereby to allow the latter to cure in optimal fashion and secure properly the respective cable bolts within their respective boreholes at the bolts"" distal ends.
2. Statement of Related Art
There is a great deal of prior art in the general field of cable bolts and their design, as well as torquing equipment for cable bolts. As to the present invention, the following art is noted: the article in xe2x80x9cWire Rope New and Sling Technology,xe2x80x9d p. 56 (citing U.S. Pat. No. 5,741,092), October 1998; also, U.S. Pat. Nos. 906,040; 1,590,200; 3,161,090; 3,940,941; 5,531,545 (the inventor herein being patentee); U.S. Pat. Nos. 5,511,909; 5,230,589; 5,259,703 and 5,951,064. Many additional patents and other literature are cited in these references as background, all of which are fully incorporated herein by way of reference.
The art of introducing resin system capsules in a mine borehole and then advancing these to the blind end of a borehole by a cable bolt backing the capsules is well known. The spinning of the cable bolt ruptures the capsules and mixes the resin system supplied. The mixing should continue until the resin has a particular viscosity, but should not be overmixed. Otherwise, the holding power of the resin, now disposed between the cable bolt shank and the wall of the borehole, will become lessened. Failure can occur, either when the cable bolt plus resin, pulls out of the hole when the bolt is placed in tension, or when the bolt simply pulls through the resin sleeve, or when simply the resin does not make a secure anchor with the surrounding strata of the borehole. Manufacturers specify optimal mixing time needed to achieve the viscosity desired and, hence, the point of maximum holding power. The present invention precludes the optimal mixing from being exceeded, by supplying a relief feature whereby the cable bolt is not spun further once a particular torque resistance level is reached. None of the above art and references, taken either singly or in combination, is believed to anticipate this invention as described below.
The invention resides in the combination, and also in the individual constituents therein, of a cable bolt and a torquing tool, the latter to be secured in and revolved by conventional, installation power equipment, or simply rotated manually, whereby the cable bolt can be axially spun and thrust home, by such tool and, e.g., its power equipment, within a borehole. This is achieved by a new design of the proximal end of the cable bolt and the design of the tool by which such proximal end is engaged. Since cable bolts, owing to high-volume use, must be manufactured at low cost, reliance is made herein upon the wedge barrel of the cable bolt having an outer peripheral surface of revolution, free of radial projections, and reliance being made of either (1) designing the wedge barrel so that its outer surface is conically tapered inwardly toward said proximal end, for effecting a mutual conical frictional engagement as between the wedge barrel and the tool designed to drive the same, and/or (2) where the wedge barrel and tool have releasably inter-engaging undulations or protuberances, to effect a releasable keying of the tool to the collar, for accomplishing the spinning function, or both.
The method inherent in the invention in setting a cable bolt in a mine borehole, provided with resin, comprises the steps of: (1) providing a cable bolt having an elongated shank and a wedge barrel, provided a peripheral surface of revolution, fixed to said shank and constructed for operational, releasable engagement by a spin-and-axial-thrust providing tool; (2) providing a tool constructed and dimensioned for releasably engaging said wedge barrel in a manner whereby to axially spin said wedge barrel and thus said cable bolt through a predetermined permissible torque range and automatically to interrupt such axial spin function once said predetermined torque range is exceeded, and (3) operatively releasably engaging said tool with said wedge barrel. The over-all object of the invention is to provide, in a cable bolt structure and method of installing the same in a resin-provided borehole, both the means and the method of both spinning and thrusting home a cable bolt in its intended borehole and, in doing so, mixing the resin without chancing over-mixing the same, whereby to optimize the holding power of the resin anchor for the cable bolt.
The invention, both as to its objects and advantages, may best be understood by reference to the following description, taken in conjunction with the following drawings.